Depuration of Lead (Pb) from Nirwana Tilapia (Oreochromis niloticus) Using Coconut Cake and Palm Oil Cake Substituted Feed

Abstract

Nirwana Tilapia is not only a popular fish for consumption in Indonesia but also an important aquaculture species. Nirwana is widely cultivated in locations with different water characteristics that can make the fish contaminated by various toxic and hazardous substances, including lead (Pb). Fish have the ability to absorb and accumulate Pb from the water in their body tissues, especially the tissues of the body that contains a lot of fat and muscle tissue such as the organs of the viscera. The process of absorption and accumulation is a mechanism that is unique and different for each fish species with the level of concentration which is linear with time. The Pb compound that accumulates can bring an effect which is lethal, sub-lethal and chronic to cultured fish and may experience biomagnifications in the food chain and will have an impact on human. Therefore, it is necessary to carry out post-fish harvest treatment of the cultured fish to clean up or reduce the concentration of Pb. The cleaning up or Pb reduction of fish can be done by depuration. The depuration method used in this research was by providing coconut cake and palm oil cake as substituted feed which have the ability to absorb Pb from the body tissues of fish since coconut cake and palm oil cake are actually vegetable materials that generally have coarse fiber and high fat. The coarse fiber in the diet is needed to assist in the digestion of food. The fat in the feed is expected to absorb large amounts of heavy metals deposited in the body tissues of fish. This study aimed to analyze the potential of coconut cake and palm oil cake for Pb depuration of nirwana. The research result would be benefitial information for farmers and the community of tilapia fishery, especially on the use of local products as alternative feed ingredients to improve food security through depuration mechanism. The treatments in this study were 100% commercial feed (Pk), 30% coconut cake + 70% commercial feed (PBB) and 30% palm oil cake + 70% commercial feed (PBS). The nirwana tilapia used with a weight of 100 ± 15 g. 10 fish were put in each plastic drum container corresponding with the number of treatments (3 treatments and 3 replications). Test fish were injected with 1 mg/L Pb(NO3)2 intraperitoneally. Each test animal was fed at satiation twice a day for eight days. The sampling was done on days two, four, six and eight. Parameters observed were Pb content in flesh, feces and water used in the raising activity, proximate flesh to find out the content of fat and coarse fiber in the fish flesh, histochemistry in liver and kidney, survivability, growth rate and water quality. The data analysis used was ANOVA and descriptive. AAS analysis results on flesh and feces proved that most of the Pb was excreted through feces. The highest concentration of Pb excreted through feces was in PBS treatment (1.46 mg/kg), while on days two, four, six and eight, the Pb concentrations were less than 0.001 mg/kg. The highest content of dietary fat on treatment PBK was 13.33% and PBS 4.78% with crude fiber content of PBK 0.38% and PBS 7.23%. These results indicated that coconut cake and palm Oil cake-substituted Feed was used as depuration agents that successfully reduced a large amount of xenobiotic Pb from the fish tissue via their feces.